Escherichia coii enzyme

Fig. 1. The active sites of PT SI and of the A subunits of diphtheria toxin and Escherichia coii heat labile toxin. The thin lines represent the carbon backbones. Only those (3 strands and a helices that are relevant for the active-site geometry are shown. The side chains of residues involved in the enzyme activity, especially those of the catalytic Glu and His residues, are represented by the thick lines. The a2 helix present in PT (top) and coii heat labile toxin (LT, right) is completely missing in diphtheria toxin (DT, left)...

Figure 12 Glycoengineering in Escherichia coii using Campylobacter jejuni protein N-glycosylation and N. meningitidis protein O-glycosylation systems. E. coli cells are transformed with a gene encoding a protein acceptor (purple), an OTase (yellow) and a gene cluster encoding the enzymes required for the synthesis of the glycan of interest.

Figure 19 Close-up view of the solvent-filled vestibule in Escherichia coii CTP synthetase, which is proposed to form part of the ammonia tunnel in the enzyme (1S1M). Red spheres indicate water molecules, and the glutaminase and synthetase domains are colored blue and green, respectively. Residues in the flexible loop (L11) are colored gray, while those lining the tunnel are represented as sticks . Coloring C - gray, O - red, N - blue, and S - yellow. Image rendered in PYMOL.

Figure 8 Biosynthesis of thiamine pyrophosphate in Escherichia coii. The two radicai SAM enzymes invoived in this process are highiighted in red. P = phosphate group.

Phosphomycin, introduced in 1972, inhibits enolpyruvial transferase, an enzyme catalyzing an early step in bacterial cell wall biosynthesis. Inhibition results in reduced synthesis of peptidoglycan, an important component in the bacterial cell wall. Phosphomycin is bactericidal against Escherichia coii and Enterobacter faecaiis infections. 

Resistance is mediated by several R-factor enzymes that catalyze acetylation of the secondary and, to some extent, the primary hydroxyl groups in the aliphatic side chain. These products no longer bind to the ribosomes and so are inactivated. Escherichia coii frequently is resistant because of chloramphenicol s lack of intercellular accumulation. 

Beacham, I.R., Haas, D. and Yagil, E. (1977) Mutants of Escherichia coii cryptic for certain periplas-mic enzymes evidence for an alteration of the outer membrane. Journai of Bacterioiogy 129, 1034-1044. 

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